Electrical equipment may not perform correctly if undesirable electrically conducting paths form between circuit elements at different electrical potentials. Installations with low voltage circuitry such as telephone exchanges and computer rooms are particularly vulnerable. Electrically conducting paths may form when airborne, electrically conductive particles settle upon circuit elements. For example, zinc particles or “whiskers” are known to grow on zinc electroplated metalwork used in such installations. If a whisker breaks away from the metalwork, the result is an extremely light, virtually invisible, needle-like and highly electrically conductive, airborne whisker. This whisker may fall upon sensitive electronic circuitry, resulting in equipment failure. This mode of failure is known to occur in many installations, yet can be particularly difficult to diagnose. Failure due to metallic whiskers is an ongoing problem which is extremely costly for providers of data processing and switching equipment. It is desired, therefore, to provide a device for detecting an electrically conductive particle, or at least a useful alternative to existing detection devices.